Aswin Kumar Ilango

Innovative approaches are urgently needed to improve the phytoremediation of complex mixtures of per- and polyfluoroalkyl substances (PFAS) in contaminated soils. This study investigated the effectiveness of plant growth regulators (PGRs) in enhancing the uptake of a mixture of eight PFAS (100 μg/kg each) by Timothy grass (TG) from soil. A suite of PGRs including auxins (indole-3-acetic acid [IAA], indole-3-butyric acid [IBA]), gibberellic acid (GA), jasmonic acid, α-naphthaleneacetic acid, and 2,4-dichlorophenoxyacetic acid) was applied individually via foliar spray at concentrations ranging from 0.1 to 200 μM. Among all treatments, IBA at 10 μM (IBA-10), IAA-1, and GA at 0.1–1 μM significantly enhanced shoot accumulation of PFHxA and PFHpA, with maximum uptake reaching ∼23% in TG during the second harvest (days 55–108). Compared to the controls without exposure to PGRs, this enhancement was ∼63%. In addition, PGRs enhanced the translocation of long-chain PFOS and PFNA, with increases of 45–82% over the controls. Uptake of ΣPFAS peaked around 7–9% of the total spiked mass for those with IBA-10, IAA-1, or GA-1/GB-0.1, underscoring the importance of type and concentration of PGRs in enhancing phytoextraction. Similar results were also observed for alfalfa undergoing similar treatment with PGRs. Insight from both TG and alfalfa indicates that not all PGR applications led to enhanced biomass weight and PFAS uptake percentage. Some treatments increased tissue PFAS concentrations without improving biomass dry weight, while others enhanced biomass but resulted in only modest increases in PFAS translocation. These results demonstrate that some foliar-applied phytohormones can regulate PFAS accumulation in plants, offering a potential strategy to improve phytoextraction efficiency. The underlying mechanisms, however, will need to be further elucidated.

Per- and polyfluoroalkyl substances (PFAS) present in biosolids pose challenges for the management of biosolids land application. This study evaluated the phytoremediation potential of a grass-legume mixture derived from a Conservation Reserve Program (CRP) seed blend for removing PFAS from biosolids-amended soils treated with biochar. Thirteen representative PFAS were monitored in plant tissues over a 92 day greenhouse experiment. Results showed that PFAS uptake was significantly influenced by soil type, biochar type and dose, and biosolids characteristics. Notably, biosolids derived from a mixture of industrial and domestic wastewater, containing higher concentrations of PFAS precursors (1515.9 ± 1.89 μg/kg), resulted in reduced plant biomass and lower ΣPFAS removal of 0.3-0.7% compared to 1.0-2.5% of ΣPFAS removal with biosolids comprising PFAS precursors of 6.30 ± 1.89 μg/kg sourced solely from domestic wastewater. While low-dose biochar (0.05%) enhanced PFAS uptake under certain conditions, higher doses (5%) generally stabilized PFAS, reducing their bioavailability. Isotopically labeled PFHxS and PFNA confirmed these patterns, with chain length influencing uptake efficiency. Leaching tests using water revealed that biochar amendments reduced PFAS leachability in Scantic soil but increased it in Woodbridge soil, highlighting the need for site-specific remediation strategies. Overall, PFAS phytoextraction was less effective in biosolids derived from mixed industrial and domestic sources compared with those from domestic wastewater alone. This study highlights the importance of tailoring phytoremediation and biochar applications to biosolids composition and soil properties to ensure safe and effective PFAS management.

Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic chemicals of global concern, and adsorption remains one of the most efficient methods for their removal from water. The present research reported a new kind of graphene nanoplatelets (GNP) modified by a cationic surfactant, cetyltrimethylammonium chloride (CTAC). This GNP-CTAC was observed to achieve nearly 100% capture of all 10 target PFAS, each at 10 μg/L in Milli-Q water. The pseudo-second-order model most accurately represented the adsorption kinetics, which was realized as a fast adsorption process in less than 1 min. The Sips isotherm model effectively fits the isotherm data, indicating that the adsorption of PFAS onto GNP-CTAC involved both heterogeneous surface sites and multilayer adsorption driven by combined electrostatic and hydrophobic interactions. The hypothesized adsorption mechanisms, including electrostatic and hydrophobic interactions, were validated by detailed physicochemical characterization. Remarkably, the performance of GNP-CTAC remained unaffected by variations in solution pH, ionic strength, natural organic matter, and nearly 100% removal effectiveness of PFAS in river water (surpassing conventional adsorbents like powdered activated carbon) at an initial PFAS concentration of 200 ng/L. Importantly, the adsorption performance of GNP-CTAC was successfully validated through a third-party evaluation. Along with its rapid adsorption of PFAS and stability across various water qualities, GNP-CTAC was also regenerable and could be reused for a minimum of four cycles, retaining most of its adsorption performance. Notably, stability evaluations confirmed that CTAC remained attached to the GNP surface during regeneration and adsorption, with no signs of surfactant leakage.

Per- and polyfluoroalkyl substances (PFAS), a diverse range of anthropogenic organic compounds, pose significant concerns to society due to their potential harmful impacts on human health and ecosystems. While there are other methods for removing PFAS from water, adsorption remains a viable and efficient option. The present research reports an adsorptive nanofiber membrane prepared through electrospinning in the presence of poly­(vinyl alcohol) (PVA) and a cationic surfactant, cetyltrimethylammonium chloride (CTAC), blended solution. This modified PVA membrane was observed to achieve nearly 100% capture of all 10 target PFAS, each at 10 μg/L in deionized water. The pseudo-second-order model most accurately represented the adsorption kinetics, characterized by rapid adsorption (within 60 s). The Toth isotherm model effectively fitted the isotherm data, indicating that the adsorption of PFAS onto the membrane involved complex interactions. The hypothesized adsorption mechanisms, including electrostatic and hydrophobic interactions, were validated through detailed adsorption kinetics, isotherms, thermodynamic analyses, and physicochemical characterization. Remarkably, the performance of the modified system remained unaffected by variations in solution pH and natural organic matter, while being slightly affected by ionic strength, with 90–100% removal effectiveness of PFAS in stormwater. This work highlights the significance of electrospun nanofiber membrane-based adsorbents for the efficient removal of PFAS from real water.

Per- and polyfluoroalkyl substances (PFAS) make up a diverse group of industrially derived organic chemicals that are of significant concern due to their detrimental effects on human health and ecosystems. Although other technologies are available for removing PFAS, adsorption remains a viable and effective method. Accordingly, the current study reported a novel type of graphene oxide (GO)-based adsorbent and tested their removal performance toward removing PFAS from water. Among the eight adsorbents tested, GO modified by a cationic surfactant, cetyltrimethylammonium chloride (CTAC), GO-CTAC was found to be the best, showing an almost 100% removal for all 11 PFAS tested. The adsorption kinetics were best described by the pseudo-second-order model, indicating rapid adsorption. The isotherm data were well supported by the Toth model, suggesting that PFAS adsorption onto GO-CTAC involved complex interactions. Detailed characterization using scanning electron microscopy-energy dispersive X-ray spectroscopy, Fourier transform infrared, thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy confirmed the proposed adsorption mechanisms, including electrostatic and hydrophobic interactions. Interestingly, the performance of GO-CTAC was not influenced by the solution pH, ionic strength, or natural organic matter. Furthermore, the removal efficiency of PFAS at almost 100% in river water demonstrated that GO-CTAC could be a suitable adsorbent for capturing PFAS in real surface water.

Fluorosis is a health problem that affects many people worldwide. To solve this problem, we developed a hybrid composite using magnesia dispersed in hybrid biopolymers (pectin and alginate), which was doped with lanthanum (La) or cerium (Ce) to yield pectin-alginate-magnesia-lanthanum (PAML) and pectin-alginate-magnesia-cerium (PAMC) hybrid composites, respectively, for efficient fluoride removal. The fabricated PAML and PAMC composites were characterized by SEM, FTIR, and EDAX studies. The manipulating factors such as dosage, pH, reaction time, initial ion concentration, temperature, and co-ions were examined under batch method. In this exploration, fluoride adsorption onto the PAML and PAMC composites was studied to illuminate the defluoridation mechanism. The PAML and PAMC composites revealed that fast kinetics was reached within 30 min. Fluoride adsorption on the PAML and PAMC composites was in accordance with the Langmuir isotherm model, with an enhanced defluoridation capacities (DCs) of 4961 and 4957 mgF⁻ kg⁻¹ respectively within 30 min at pH 6.0, respectively. Based on the characterization data and experimental results, it was determined that complexation and electrostatic interaction contributed to the fluoride capture route. Moreover, the developed PAML and PAMC composites are reusable and suitable for real water sample analysis.

The magnetic hybrid material, namely, iron oxide/alginate–gelatin/hydroxyapatite/covalent organic framework (MAGHCOF)-based bio-hybrid beads were prepared and utilized for fluoride removal studies.